Drive system for industrial machinery

Abstract

To provide a drive system for work machinery that can reduce the load on the reduction gear. [Solution] The drive system 30 of the excavator 100, which is a work machine, comprises an electric motor 40, a reduction gear 50, a control device 90, and a temperature sensor TS. The reduction gear 50 is connected to the electric motor 40. The reduction gear 50 amplifies the torque of the electric motor 40 and outputs it to the object to be driven. The control device 90 supplies power to the electric motor 40. The temperature sensor TS detects the temperature of the reduction gear 50. When the temperature detected by the temperature sensor TS is below a predetermined specified temperature, the control device 90 performs a warm-up process by supplying power to the electric motor 40. The control device 90 performs the warm-up process while keeping the rotation angle of the output shaft of the reduction gear 50 within a predetermined range.

Description

Technical Field

[0001] The present invention relates to a drive system for a work machine.

Background Art

[0002] A hydraulic excavator, which is a work machine disclosed in Patent Document 1, includes a lower traveling body and an upper revolving body that are drive targets. The hydraulic excavator drives the lower traveling body by means of a traveling hydraulic motor and a speed reducer. The hydraulic excavator causes the upper revolving body to revolve relative to the lower traveling body by means of a revolving hydraulic motor and a speed reducer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a drive system for a work machine that drives the work machine, the lubricating function of the lubricant in the speed reducer may deteriorate as the temperature of the speed reducer decreases. Accordingly, in the drive system for a work machine, it is desired to warm the lubricant in the speed reducer at an early stage to reduce the load applied to the speed reducer when the drive target is rotated.

Means for Solving the Problems

[0005] A drive system for a work machine to solve the above problems comprises an electric motor, a reduction gear connected to the electric motor that amplifies the torque of the electric motor and outputs it to the object to be driven, a control device that controls the power supply to the electric motor, and a temperature sensor that detects the temperature of the reduction gear. When the temperature detected by the temperature sensor is below a predetermined specified temperature, the control device performs a warm-up process to heat up the electric motor by supplying power to it while keeping the rotation angle of the output shaft of the reduction gear within a predetermined range.

[0006] According to the above configuration, the drive system of the work machine generates heat in the electric motor while keeping the object to be driven within a predetermined range of rotation through the warm-up process of the control device. The heat from the electric motor is transferred to the reduction gear connected to the electric motor. The drive system of the work machine can supply power to the electric motor until the reduction gear reaches a specified temperature while keeping the rotation of the object to be driven within a predetermined range. In other words, the drive system of the work machine can raise the reduction gear above a predetermined specified temperature by generating heat in the electric motor. Therefore, the drive system of the work machine can reduce the load on the reduction gear.

[0007] In a drive system for a work machine, the reduction gear has a housing, the electric motor has a heat transfer shaft that extends coaxially with the output shaft of the electric motor and penetrates the output shaft of the electric motor, the heat transfer shaft reaches the inside of the housing, and the thermal conductivity of the heat transfer shaft may be higher than that of the output shaft of the electric motor.

[0008] In the drive system of the work machine, the heat transfer shaft can be switched between an inserted state in which its tip is located inside the housing and an uninserted state in which its tip is located outside the housing, and the control device may switch the heat transfer shaft to the inserted state during the warm-up process.

[0009] In the drive system of the work machine, a thermal transistor is interposed between the electric motor and the reduction gear, and the thermal transistor can be switched between a high thermal conductivity state, which has higher thermal conductivity than the material of the output shaft of the electric motor, and a low thermal conductivity state, which has lower thermal conductivity than the high thermal conductivity state, and the control device may switch the thermal transistor to the high thermal conductivity state during the warm-up process.

[0010] In a drive system for a work machine, when one of the output shafts of the electric motor and the output shaft of the reduction gear is selected as the restricted shaft, the system includes a brake device that can switch between a restricting state in which the brake device contacts the restricted shaft to restrict its rotation and a permissible state in which the rotation of the restricted shaft is permitted, and the control device may switch the brake device to the restricting state during the warm-up process.

[0011] In a drive system for a work machine, the system comprises a plurality of electric motors, a plurality of reduction gears corresponding to each of the plurality of electric motors, and a plurality of temperature sensors corresponding to each of the plurality of reduction gears, and the control device may independently perform the warm-up process for each of the electric motors.

[0012] In a drive system for a work machine, a clutch mechanism is interposed between the electric motor and the reduction gear, and is switchable between a disengaged state that disconnects the electric motor and the reduction gear, and an engaged state that allows torque transmission from the electric motor to the reduction gear. The control device may switch the clutch mechanism to the disengaged state during the warm-up process. [Effects of the Invention]

[0013] This reduces the load on the gearbox. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a schematic side view of an excavator. [Figure 2] Figure 2 is a top view schematically illustrating an excavator. [Figure 3] Figure 3 is a diagram illustrating a drive system. [Figure 4] Figure 4 is a diagram illustrating one drive unit in the drive system. [Figure 5] Figure 5 is a diagram illustrating one drive unit in the drive system according to the second embodiment. [Figure 6] Figure 6 is a diagram illustrating one drive unit in the drive system according to the third embodiment. [Mode for Carrying Out the Invention]

[0015] <First Embodiment> Hereinafter, one embodiment of the drive system for a work machine will be described. In the present embodiment, the drive system for a work machine is embodied and described as a drive system for an excavator. That is, in the present embodiment, the work machine is an excavator. In the following, the drive system of the excavator is simply referred to as the "drive system". The drawings may show components in an enlarged scale for ease of understanding. Further, the dimensional ratios of the components may differ from the actual ones or those in other drawings.

[0016] <Overall Configuration of Excavator> As shown in Figure 1, the excavator 100 includes a main body 10 and a work attachment 20. The excavator 100 also has a drive system 30. The drive system 30 of the excavator 100 drives the main body 10 and the work attachment 20.

[0017] <Main Body> The main body 10 includes a lower travel body 13, an upper swing body 14, and a swing bracket 17. The main body 10 constitutes the vehicle body of the excavator 100. The lower travel body 13 is the portion of the main body 10 that is in contact with the ground G. The upper swing body 14 is located on the side opposite to the ground G with respect to the lower travel body 13.

[0018] In the main body portion 10, the lower body 13 and the upper body 14 are arranged side by side in one direction. In the present embodiment, in the main body portion 10, the direction from the lower body 13 toward the upper body 14 is the upward direction, and the opposite direction is the downward direction. A specific direction among the directions orthogonal to the upward direction is the front direction, and the opposite direction is the rear direction. One of the directions orthogonal to both the upward direction and the front direction is the left direction, and the other is the right direction. The front direction and the rear direction may be collectively referred to as the X direction. The left direction and the right direction may be collectively referred to as the Y direction. The upward direction and the downward direction may be collectively referred to as the Z direction.

[0019] As shown in FIG. 1 and FIG. 2, the lower body 13 has a rectangular parallelepiped shape, for example. The main body portion 10 is provided with a pair of travel devices 12 on the lower body 13. The excavator 100 travels by the pair of travel devices 12. In FIG. 1, only one of the pair of travel devices 12 is illustrated by a two-dot chain line. Both of the pair of travel devices 12 are connected to the lower body 13. The travel device 12 includes a crawler and travel rollers 12A that cause the crawler to circulate. The excavator 100 travels by causing the crawler to circulate while keeping it in contact with the ground. The travel roller 12A rotates about a travel axis J5 as its axis.

[0020] The upper body 14 includes a main housing portion 14A and a front housing portion 14B. The main housing portion 14A constitutes most of the upper body 14. The main housing portion 14A is a portion of the upper body 14 that includes a cabin (not shown). The cabin is a portion on which an operator who operates the excavator 100 rides. The main housing portion 14A accommodates various devices for operating the excavator 100. The front housing portion 14B is located on the front direction side with respect to the main housing portion 14A. The front housing portion 14B is fixed to the front face of the main housing portion 14A.

[0021] As shown in FIG. 1, the main body portion 10 is provided with a slewing bearing 18. The slewing bearing 18 is located between the lower body 13 and the upper body 14. In FIG. 1, the width of the slewing bearing 18 in the Z direction is exaggerated and illustrated to be large.

[0022] As shown in Figure 2, the slewing bearing 18 is an annular body with its central axis being the slewing axis J6. The slewing bearing 18 comprises an inner ring 18A fixed to the lower body 13, an outer ring 18B fixed to the upper body 14, and a plurality of rolling elements (not shown). The central axes of the inner ring 18A and the outer ring 18B are the slewing axis J6. The inner ring 18A and the outer ring 18B are connected by a plurality of rolling elements such that one can rotate relative to the other. As a result, one of the upper body 14 and the lower body 13 can rotate relative to the other.

[0023] As shown in Figures 1 and 2, the swing bracket 17 is located at the front of the housing 14B. The swing bracket 17 comprises a first swing wall 17A and a second swing wall 17B. The first swing wall 17A is connected to the front of the housing 14B. The first swing wall 17A is a disc-shaped body with its thickness in the Z direction. The second swing wall 17B protrudes upward from the upper surface of the first swing wall 17A. The second swing wall 17B is a plate-shaped body with its thickness in the Y direction.

[0024] The first swing wall 17A, together with the second swing wall 17B, is rotatable around the front of the housing 14B about a fourth axis J4 that extends in the Z direction. The fourth axis J4 is approximately parallel to the pivot axis J6.

[0025] <Work Attachment> As shown in Figure 1, the work attachment 20 comprises a boom 21, an arm 23, and a bucket 25.

[0026] The boom 21 is located on the front side of the main housing portion 14A. The boom 21 is a long, plate-like or columnar body. The boom 21 comprises a first boom end 21A connected to the second swing wall 17B, and a second boom end 21B located on the opposite side of the first boom end 21A in the longitudinal direction of the boom 21. The first boom end 21A is aligned with the second swing wall 17B in the thickness direction of the second swing wall 17B.

[0027] As shown in Figure 2, the boom 21 is rotatable with respect to the second swing wall 17B, with the axis extending in the direction in which the second swing wall 17B and the first boom end 21A are aligned being its central axis. Hereafter, the axis along which the boom 21 rotates with respect to the second swing wall 17B will be referred to as the first axis J1. The first axis J1 extends in a direction approximately perpendicular to the slewing axis J6.

[0028] Arm 23 is connected to the second boom end 21B. Arm 23 is a long, plate-like or columnar body. Arm 23 comprises a first arm end 23A connected to the second boom end 21B, and a second arm end 23B located on the opposite side of the first arm end 23A in the longitudinal direction of arm 23.

[0029] The arm 23 is rotatable relative to the boom 21 with respect to the axis extending in the direction in which the first arm end 23A and the second boom end 21B are aligned. Hereafter, the central axis of rotation of the arm 23 relative to the boom 21 will be referred to as the second axis J2. The second axis J2 extends approximately parallel to the first axis J1.

[0030] The bucket 25 is located near the second arm end 23B of the arm 23. The bucket 25 comprises a bucket body 26, a plurality of claw portions 27, and a bucket connecting wall 28. The bucket body 26 is a box-shaped body that opens in one direction. The plurality of claw portions 27 protrude from one of the opening edges of the bucket body 26. In this embodiment, there are four claw portions 27. The bucket connecting wall 28 protrudes from the outer wall of the bucket body 26, on the opposite side of the opening from the claw portions 27. The bucket connecting wall 28 is a plate-shaped body.

[0031] Bucket 25 is aligned with and connected to the second arm end 23B in the thickness direction of the bucket connecting wall 28 at the bucket connecting wall 28. The bucket connecting wall 28 is rotatable about an axis extending in the direction in which the second arm end 23B and the bucket connecting wall 28 are aligned. In other words, bucket 25 is rotatable relative to arm 23. Hereafter, the central axis of rotation of bucket 25 relative to arm 23 will be referred to as the third axis J3. The third axis J3 extends approximately parallel to the first axis J1 and the second axis J2, respectively.

[0032] <Drive System> As shown in Figure 3, the drive system 30 comprises a battery 31, a plurality of drive units A, and a control device 90. Furthermore, each drive unit A comprises a plurality of electric motors 40, a plurality of reduction gears 50, a plurality of temperature sensors TS, a plurality of impact sensors IS, a plurality of angle sensors AS, and a plurality of cooling devices 60. Each drive unit A also comprises a plurality of brake devices 70 and a plurality of clutch mechanisms 80. In this embodiment, the drive unit A is a single unit in which the electric motors 40, reduction gears 50, temperature sensors TS, impact sensors IS, and angle sensors AS, as well as the cooling devices 60, brake devices 70, and clutch mechanisms 80 are integrated. The drive system 30 drives the excavator 100 through the cooperation of the plurality of drive units A and the control device 90.

[0033] The drive system 30 includes a plurality of drive units A, namely a first drive unit A1, a second drive unit A2, a third drive unit A3, a fourth drive unit A4, a travel drive unit A5, and a turning drive unit A6. Hereafter, components common to each drive unit A will be collectively referred to as drive unit A, and when it is necessary to distinguish between each drive unit A, they will be described separately as the first drive unit A1 to the turning drive unit A6.

[0034] As shown in Figure 2, the first drive unit A1 is interposed between the second swing wall 17B and the first boom end 21A. The first drive unit A1 rotates the boom 21 relative to the second swing wall 17B. The second drive unit A2 is interposed between the second boom end 21B and the first arm end 23A. The second drive unit A2 rotates the arm 23 relative to the boom 21. The third drive unit A3 is interposed between the second arm end 23B and the bucket connecting wall 28. The third drive unit A3 rotates the bucket 25 relative to the second arm end 23B. The travel drive unit A5 is located in the travel device 12. The travel drive unit A5 rotates the travel roller 12A relative to the lower body 13. The excavator 100 is equipped with a pair of travel drive units A5, but only one of the pair of travel drive units A5 is shown in Figure 3.

[0035] As shown in Figure 1, the fourth drive unit A4 is located at the front of the housing 14B. The fourth drive unit A4 rotates the first swing wall 17A relative to the front of the housing 14B. The slewing drive unit A6 is interposed between the lower body 13 and the upper body 14. The slewing drive unit A6 rotates the upper body 14 relative to the lower body 13.

[0036] <Related to electric motors> In the following sections, the configuration of each of the multiple drive units A shown in Figure 3 will be described. The description of drive units A is similar for the first drive unit A1, the second drive unit A2, the third drive unit A3, the fourth drive unit A4, the driving drive unit A5, and the turning drive unit A6.

[0037] As shown in Figure 4, the drive unit A is equipped with an inverter 32. The inverter 32 converts the DC power supplied from the battery 31 into AC power and outputs it. The drive unit A is connected to the electric motor 40. The inverter 32 may be integrated with the electric motor 40. Note that Figure 4 is a diagram focusing on one of the multiple drive units A shown in Figure 3. Figure 4 shows the common configuration that each of the multiple drive units A has, excluding the battery 31. In other words, the drive system 30 is equipped with an inverter 32 for each drive unit A. The multiple drive units A are connected to one battery 31. The battery 31 and the inverter 32 are housed in the upper body 14 of the excavator 100, for example, as shown in Figure 1.

[0038] As shown in Figure 4, the electric motor 40 is electrically connected to the battery 31 via an inverter 32. The electric motor 40 is a three-phase AC motor. Power is supplied to the electric motor 40 from the battery 31. The electric motor 40 comprises a motor housing 41 and an output shaft 42 that is rotatable relative to the motor housing 41. The motor housing 41 is attached to one of the following parts of the excavator 100: the second swing wall 17B, the second boom end 21B, the second arm end 23B, the front of the housing 14B, the main body of the housing 14A, and the lower body 13. The object to which the motor housing 41 is attached depends on which of the multiple drive units A the drive unit A containing the motor housing 41 is. For example, if the drive unit A is the second drive unit A2, the motor housing 41 is attached to the second boom end 21B, as shown in Figure 2.

[0039] The output shaft 42 protrudes from the inside to the outside of the motor housing 41. The output shaft 42 is cylindrical. The output shaft 42 is rotatable relative to the motor housing 41 about axis J, which is the central axis of the output shaft 42. That is, the output shaft 42 outputs torque about axis J. The output shaft 42 is rotatable in both forward and reverse directions about axis J.

[0040] Axis J is one of the first to fourth axis J1 to J4, the travel axis J5, and the slewing axis J6. The axis J of the electric motor 40 equipped in the first drive unit A1 is the first axis J1. The axis J of the electric motor 40 equipped in the second drive unit A2 is the second axis J2. The axis J of the electric motor 40 equipped in the third drive unit A3 is the third axis J3. The axis J of the electric motor 40 equipped in the fourth drive unit A4 is the fourth axis J4. The axis J of the electric motor 40 equipped in the travel drive unit A5 is the travel axis J5. The axis J of the electric motor 40 equipped in the slewing drive unit A6 is the slewing axis J6.

[0041] <Reducer> The reduction gear 50 comprises a gear housing 51, a reduction mechanism 52, and an output member 53.

[0042] The gear housing 51 is the housing for the reduction gear 50. The gear housing 51 is fixed to the motor housing 41. In this way, the reduction gear 50 is connected to the electric motor 40. The gear housing 51 houses the reduction mechanism 52 inside.

[0043] Torque is input to the reduction gear 52 from the output shaft 42 of the electric motor 40. The reduction gear 52 amplifies the torque from the electric motor 40 at a predetermined ratio and outputs it to the output member 53. The reduction gear 52 is, for example, an eccentric oscillating gear type or a planetary gear type.

[0044] A lubricant 52a is present inside the reduction mechanism 52. Specifically, the lubricant 52a is housed in the gear housing 51 and fills gaps between gears and other components within the reduction mechanism 52. The lubricant 52a is, for example, grease or oil. The lubricant 52a flows within the gear housing 51 as the reduction mechanism 52 operates. The lubricant 52a is intended to reduce friction between parts that slide against each other in the reduction mechanism 52. The lubricant 52a also serves as part of the heat conduction pathway between gears and other components within the reduction mechanism 52. In Figures 4 to 6, the lubricant 52a is schematically represented by a dashed line.

[0045] The output member 53 is cylindrical. The central axis of the output member 53 is approximately coincident with axis J. The output member 53 is rotatable relative to the gear housing 51. The output member 53 rotates about axis J in accordance with the rotation of the output shaft 42 of the electric motor 40. An object to be driven is attached to the output member 53.

[0046] The object to be driven is one of the following from the excavator 100: the boom 21, the arm 23, the bucket 25, the first swing wall 17A, the inner ring 18A of the slewing bearing 18, and the traveling roller 12A. Which of the above-mentioned components is the object to be driven depends on which of the multiple drive units A the drive unit A equipped with the output member 53 is. For example, if the drive unit A is the second drive unit A2, the object to be driven is the arm 23, as shown in Figure 2.

[0047] The output member 53 inputs torque around axis J to the object to be driven. In other words, the reduction gear 50 amplifies the torque of the electric motor 40 and outputs it to the object to be driven. The object to be driven receives this torque and rotates around axis J. For this reason, the electric motor 40 can be said to be a driving source for the rotating object to be driven.

[0048] <Temperature sensors, shock sensors, and angle sensors> As shown in Figure 3, the temperature sensor TS is mounted on the gear housing 51. The temperature sensor TS is located in the part of the gear housing 51 closer to the electric motor 40.

[0049] The temperature sensor TS detects the temperature of the speed reducer 50. More specifically, the temperature of the speed reducer 50 is the temperature of the gear housing 51 that the speed reducer 50 is equipped with. The temperature of the gear housing 51 reflects the temperature of the lubricant 52a contained inside the gear housing 51. Therefore, by detecting the temperature of the gear housing 51, the temperature sensor TS can also be said to detect information related to the temperature of the lubricant 52a. The temperature sensor TS repeatedly outputs the detected temperature to the control device 90 at a predetermined control cycle.

[0050] The impact sensor IS is mounted on the gear housing 51. The impact sensor IS detects impacts. The impact sensor IS is an acceleration sensor that detects the acceleration of the reduction gear 50 or the driven object as an impact. In this embodiment, the impact sensor IS detects the acceleration of the reduction gear 50 as an impact. More specifically, the impact sensor IS detects the acceleration generated in the reduction gear 50 when an impact is applied to the reduction gear 50. The impact sensor IS detects the acceleration components in the X, Y, and Z directions that occur at the mounting location. Note that the direction of acceleration detected by the impact sensor IS is not limited to the three directions described above. The impact sensor IS can be any three-axis acceleration sensor capable of detecting acceleration in three directions that are different from each other.

[0051] The impact sensor IS is powered by the auxiliary battery 33. The auxiliary battery 33 supplies power to the impact sensor IS. In other words, the drive system 30 includes the auxiliary battery 33 and powers the impact sensor IS with the auxiliary battery 33. The auxiliary battery 33 is separate from the battery 31. That is, the auxiliary battery 33 can supply power to the impact sensor IS connected to it independently of the battery 31.

[0052] The drive system 30 is equipped with one auxiliary battery 33 for each impact sensor IS. In this embodiment, the auxiliary battery 33 is a coin-type battery. The auxiliary battery 33 is mounted in the same housing as the impact sensor IS. In other words, the auxiliary battery 33 is located in the same place as the impact sensor IS within the gear housing 51.

[0053] The impact sensor IS is configured to store the detected acceleration as time-series data. The impact sensor IS stores the history of acceleration detected during the period when power is supplied from the auxiliary battery 33. The impact sensor IS may be implemented as two separate components: a detection unit for detecting acceleration and a storage unit for storing the history of detected acceleration. In this case, the impact sensor IS consists of a unit formed by the separate detection unit and storage unit. In this case, both the detection unit and the storage unit are powered by the auxiliary battery 33.

[0054] When the control device 90 is running, the impact sensor IS repeatedly outputs the detected acceleration to the control device 90 at a predetermined control cycle. When the control device 90 is not running, the impact sensor IS stores the history of detected acceleration. Then, when the control device 90 starts running, it outputs the stored acceleration history to the control device 90 as time-series data.

[0055] The angle sensor AS detects information regarding the angular position of the corresponding electric motor 40 as angular information. More specifically, the angular position of the electric motor 40 is the angular position of the output shaft 42 of the corresponding electric motor 40. The angular information represents an absolute angle. For example, the angular information indicates the angular position of the electric motor 40 within a range of 0 degrees to less than 360 degrees, with a predetermined reference position of 0 degrees. Each angle sensor AS repeatedly outputs the information it has detected to the control device 90.

[0056] <Cooling device> The cooling device 60 cools the reduction gear 50. Although not shown in detail in Figure 4, the cooling device 60 may be a water-cooled type including a flow path formed inside the gear housing 51, a refrigerant flowing through the flow path, and a pump that circulates the refrigerant through the flow path. The cooling device 60 may also be an air-cooled type including a fan.

[0057] <Brake system> The brake device 70 is interposed between the electric motor 40 and the reduction gear 50. The brake device 70 is fixed to the motor housing 41 and the gear housing 51.

[0058] The braking device 70 is configured to restrict the rotation of the restricted shaft 71. The restricted shaft 71 is selected from the output shaft 42 of the electric motor 40 and the output member 53 of the reduction gear 50. In this embodiment, the restricted shaft 71 is the output shaft 42.

[0059] The brake device 70 can be switched between a restricting state in which the rotation of the restricted shaft 71 is restricted, and a permissible state in which the rotation of the restricted shaft 71 is permitted. Specifically, the brake device 70 restricts the rotation of the output shaft 42 in the restricting state and permits the rotation of the output shaft 42 in the permissible state. By switching between the restricting state and the permissible state, the brake device 70 switches between a state in the drive unit A where no torque is input from the electric motor 40 to the reduction gear 50 and a state where that torque is input.

[0060] In the restricted state, the brake device 70 contacts the restricted shaft 71 to restrict its rotation. In the restricted state, the brake device 70 physically restricts the rotation of the restricted shaft 71 by, for example, bringing a stopper (not shown) into contact with the restricted shaft 71. In the permissible state, the brake device 70 allows the rotation of the restricted shaft 71. For example, in the permissible state, the brake device 70 does not bring the stopper into contact with the restricted shaft 71. In this way, the brake device 70 equipped with a stopper switches between the restricted state and the permissible state by moving the stopper.

[0061] <Clutch mechanism> The clutch mechanism 80 is interposed between the electric motor 40 and the reduction gear 50. The clutch mechanism 80 is fixed to the motor housing 41 and the gear housing 51. The clutch mechanism 80 is configured to be able to disconnect the output shaft 42 of the electric motor 40 from the reduction gear mechanism 52 of the reduction gear 50.

[0062] The clutch mechanism 80 is switchable between a disengaged state and an engaged state. The clutch mechanism 80 is, for example, a friction clutch having a pair of friction plates. In the disengaged state, the clutch mechanism 80 disconnects the reduction gear 50 from the electric motor 40. As a result, the clutch mechanism 80 in the disengaged state stops the input of torque from the output shaft 42 to the reduction gear 52. The clutch mechanism 80 stops the input of torque by disconnecting the output shaft 42 and the reduction gear 52. Therefore, the clutch mechanism 80 restricts the input of torque to the reduction gear 52 while allowing the rotation of the output shaft 42. In the engaged state, the clutch mechanism 80 allows the transmission of torque from the electric motor 40 to the reduction gear 50. As a result, the clutch mechanism 80 in the engaged state allows the input of torque from the output shaft 42 to the reduction gear 52.

[0063] <Control device> As shown in Figure 3, the control device 90 is a computer equipped with a processing circuit. The control device 90 is located, for example, inside the upper body 14 of the excavator 100 shown in Figure 1. The control device 90 is powered by a battery 31.

[0064] The control device 90 includes a memory 91 and a CPU 92. The memory 91 includes three types: RAM, ROM, and electrically rewritable non-volatile memory. In this embodiment, these three types are collectively referred to as memory 91. The memory 91 pre-stores various programs that describe the processes to be executed by the CPU 92. The memory 91 also pre-stores various data necessary for the CPU 92 to execute these programs.

[0065] The control device 90 comprises an operation control unit 93, a warm-up unit 94, and a load estimation unit 95. Each of the operation control unit 93, the warm-up unit 94, and the load estimation unit 95 is a functional element that operates when the CPU 92 executes a program stored in the memory 91.

[0066] The control device 90 in this embodiment executes a program stored in memory 91 based on a command signal input from an operator operating the excavator 100. The command signal is input, for example, from an input terminal installed in the cabin. The control device 90 may also execute the above-described program based on something other than a command signal from the operator. For example, the control device 90 may execute the above-described program simultaneously with the start of the excavator 100.

[0067] As shown in Figure 4, the control device 90 receives information detected by the temperature sensor TS, the impact sensor IS, and the angle sensor AS. The control device 90 also outputs control signals to the inverter 32, the cooling device 60, the braking device 70, and the clutch mechanism 80.

[0068] As shown in Figure 3, the control device 90 outputs control signals to each of the multiple drive units A. More specifically, the control device 90 independently outputs control signals to the first drive unit A1, the second drive unit A2, the third drive unit A3, the fourth drive unit A4, the travel drive unit A5, and the turning drive unit A6. The control device 90 independently performs processing for each of the multiple drive units A using the operation control unit 93, the warm-up unit 94, and the load estimation unit 95.

[0069] <Operation Control Unit> The operation control unit 93 performs operation control processing that outputs control signals to the inverter 32, the brake device 70, and the clutch mechanism 80 based on input from the operator.

[0070] The inverter 32 supplies power from the battery 31 to the electric motor 40 based on the control signal input from the operation control unit 93. In other words, the control device 90 controls the power supply to the electric motor 40. The control device 90 controls the operation of the excavator 100 by controlling the power supply to the electric motor 40 in each of the multiple drive units A. For example, the control device 90 controls the movement of the excavator 100 by controlling the power supply to the electric motor 40 included in the travel drive unit A5.

[0071] The brake device 70 switches between a restricted state and a permissible state based on a control signal input from the operation control unit 93. For example, consider the case where the control device 90 switches each of the brake devices 70 of the first to third drive units A1 to A3 from a restricted state to a permissible state based on input from the operator. In this case, the excavator 100 can operate the boom 21, arm 23, and bucket 25 by rotating the electric motors 40 included in each of the first to third drive units A1 to A3.

[0072] The clutch mechanism 80 switches between a disengaged state and an engaged state based on a control signal input from the operation control unit 93. For example, consider the case where the control device 90 switches each of the clutch mechanisms 80 of the first to third drive units A1 to A3 from a disengaged state to an engaged state based on input from the operator. In this case, the excavator 100 can operate the boom 21, arm 23, and bucket 25 by inputting the rotation of the electric motor 40 included in each of the first to third drive units A1 to A3 to the reduction gear 50 included in the drive unit A.

[0073] <Warm-up section> The warm-up unit 94 performs a warm-up process to warm up each of the reduction gears 50 included in the same drive unit A as the temperature sensor TS, based on the temperature input from each of the multiple temperature sensors TS. In other words, the control device 90 performs the warm-up process.

[0074] The warm-up process is performed when the temperature detected by the temperature sensor TS is below a predetermined specified temperature. The control device 90 receives the temperatures detected by each of the multiple reduction gears 50 from the multiple temperature sensors TS. The warm-up unit 94 refers to each of the multiple input temperatures and identifies the temperature sensor TS that detected a temperature below the specified temperature. Furthermore, the warm-up unit 94 identifies the drive unit A that is equipped with the identified temperature sensor TS. The control device 90 then performs the warm-up process on the identified drive unit A using the warm-up unit 94.

[0075] The specified temperature is pre-set and stored in memory 91. The specified temperature is set based on, for example, the physical properties of the lubricant 52a contained in the reducer 50, and the type and size of the reduction mechanism 52. An example of a specified temperature is the temperature at which the resistance value to the reduction mechanism 52 is considered not to interfere with the smooth operation of the reduction mechanism 52. The specified temperature is set for each reducer 50. The specified temperature may be different for each reducer 50, or it may be the same for all reducers 50.

[0076] The warm-up process is a process of supplying power to the electric motor 40 while keeping the rotation angle of the output member 53 of the reduction gear 50 within a predetermined range. When the rotation angle of the output member 53 is within a certain range, the rotation range of the drive object attached to the output member 53 also falls within a range corresponding to the aforementioned predetermined range. Therefore, the warm-up process can also be described as a process of supplying power to the electric motor 40, which is the drive source of the drive object, while limiting the rotation range of the drive object.

[0077] In this embodiment, the control device 90 supplies power to the electric motor 40 during the warm-up process to prevent the output member 53 of the reduction gear 50, which is the target of the warm-up process, from rotating. For example, the control device 90 supplies power to the electric motor 40 in a way that prevents the output shaft 42 from rotating by adjusting the phase of the three-phase AC power supplied to the electric motor 40 using the inverter 32. Specifically, for the output shaft 42 of the electric motor 40 to rotate, the frequency of the AC power output by the inverter 32 and the rotation angle of the output shaft 42 must be linked. Therefore, by outputting AC power from the inverter 32 that is not linked to the rotation angle of the output shaft 42, the output shaft 42 can be prevented from rotating.

[0078] The above-mentioned certain range may be set based on the type and size of the object to which each reduction gear 50 outputs torque. The certain range may also be set according to the allowable operating range of the object to which the reduction gear 50 connected to the reduction gear 50 is to be warmed up during the warm-up process. It is preferable that the certain range be set small, and most preferably that it is set so that the output member 53 of the reduction gear 50 does not rotate.

[0079] The warm-up process is a process that generates heat in the electric motor 40 by supplying power to it. A portion of the power supplied to the electric motor 40 is converted into heat, for example, in the coils of the electric motor 40. In this way, the electric motor 40 generates heat due to the power supplied. The warm-up unit 94 generates heat in the electric motor 40 while restricting the rotation of the output shaft 42 by performing the warm-up process. In other words, the warm-up unit 94 generates heat in the electric motor 40 while restricting the rotation of the driven object that uses the electric motor 40 as a driving source. The heat generated in the electric motor 40 is transferred to the reduction gear 50, which leads to a temperature rise in the reduction gear 50.

[0080] The warm-up process is performed until the temperature detected by the temperature sensor TS exceeds a specified temperature. The warm-up unit 94 stops the warm-up process for the drive unit A when the temperature detected by the temperature sensor TS of the drive unit A, which is the target of the warm-up process, exceeds the specified temperature. Therefore, the warm-up process can also be described as a process in which the reduction gear 50, whose temperature detected by the temperature sensor TS is below the specified temperature, is raised to a temperature above the specified temperature by the heat generated by the electric motor 40.

[0081] Furthermore, if the control device 90 receives input from multiple temperature sensors TS indicating a temperature below a specified temperature, the warm-up unit 94 identifies all drive units A equipped with the temperature sensors TS. The warm-up unit 94 then performs a warm-up process for all identified drive units A. In other words, the control device 90 performs a warm-up process independently for each electric motor 40. The warm-up unit 94 then stops heating the electric motor 40 by the warm-up process, starting with the drive units A whose temperature detected by the temperature sensors TS exceeds the specified temperature. The warm-up unit 94 continues to perform the warm-up process for each drive unit A included in the drive system 30 until the temperature detected by the reduction gear 50 exceeds the specified temperature.

[0082] During the warm-up process, if the temperature detected by the temperature sensor TS exceeds a predetermined upper limit, the control device 90 cools the reduction gear 50 using the cooling device 60. The upper limit may be determined based on the physical properties of the lubricant 52a, or based on the upper limit of the temperature that can be allowed in the electric motor 40 and the reduction gear 50. The upper limit is a temperature higher than the specified temperature mentioned above.

[0083] <Effects of warm-up treatment> Consider the case in the excavator 100 where the temperature sensor TS detects a temperature below a specified temperature in the reduction gear 50. In this case, the drive system 30 of the excavator 100 performs a warm-up process using the control device 90. The control device 90 controls the rotation of the output member 53 of the reduction gear 50 and supplies power to the electric motor 40 to generate heat.

[0084] The heat generated in the electric motor 40 is transferred to the reduction gear 50 connected to the electric motor 40. In other words, the reduction gear 50 is heated by the heat generated in the electric motor 40 during the warm-up process. More specifically, the heat generated in the electric motor 40 during the warm-up process is transferred to the reduction gear 50 via the motor housing 41 and the output shaft 42. The heat generated in the electric motor 40 is transferred to the gear housing 51 and the reduction mechanism 52, and also heats the lubricant 52a. In other words, the warm-up unit 94 heats the lubricant 52a of the reduction gear 50 by performing the warm-up process.

[0085] The control device 90 performs a warm-up process until the temperature detected by the reduction gear 50 exceeds a specified temperature. <Load estimation section> The load estimation unit 95 performs load estimation processing on the reduction gear 50 or the object to be driven, which are included in the same drive unit A as the impact sensor IS, based on the acceleration input from each of the multiple impact sensors IS. In other words, the control device 90 performs load estimation processing.

[0086] The control device 90 receives acceleration data detected by the reduction gear 50 from impact sensors IS included in each of the multiple drive units A. The load estimation unit 95 stores the input acceleration data as time-series data for each drive unit A. Furthermore, at the start of operation of the control device 90, the control device 90 receives time-series data of acceleration data detected by the multiple impact sensors IS during periods when the control device 90 is not operating. Therefore, the control device 90 performs load estimation processing based on the acceleration data detected by the impact sensors IS at each reduction gear 50, including periods when the control device 90 is not operating.

[0087] The load estimation process calculates an estimated value of the load on the speed reducer 50 or the object being driven. In this embodiment, the load estimation process calculates an estimated value of the load on the speed reducer 50. The control device 90 performs the load estimation process for each of the multiple speed reducers 50 using the load estimation unit 95. In this embodiment, the estimated value of the load is an estimated value of the magnitude of the load torque acting on the speed reducer 50.

[0088] When the control device 90 is not supplying power to the electric motor 40, it calculates an estimated value in the load estimation process based on the impact detected by the impact sensor IS. In the load estimation process in the load estimation unit 95, the control device 90 calculates an estimated value based on the impact detected by the impact sensor IS.

[0089] The load estimation unit 95 acquires acceleration input to the control device 90 from each impact sensor IS, as well as time-series data of acceleration. In other words, the load estimation unit 95 acquires time-series data of acceleration for both operating and non-operating periods of the control device 90. The load estimation unit 95 calculates an estimated load value from the time-series data of acceleration in each reduction gear 50. The load estimation unit 95 calculates an estimated load value from the acceleration at each time point, for example, based on a table prepared in advance in memory 91. The table only needs to show the relationship between the position where the impact sensor IS is attached, the acceleration values ​​in the X, Y, and Z directions, and the load torque of the reduction gear 50. The table can be created, for example, by simulation.

[0090] When the control device 90 is supplying power to the electric motor 40, it calculates an estimated value in the load estimation process based on the current value supplied to the electric motor 40. In the control device 90, the load estimation unit 95 obtains the current value supplied from the battery 31 to the electric motor 40 of each drive unit A from the operation control unit 93. Furthermore, the load estimation unit 95 obtains angle information of the output shaft 42 from the angle sensor AS attached to the electric motor 40. After converting the angle information into the rotational speed of the output shaft 42, the load estimation unit 95 calculates an estimated value of the load torque of the reduction gear 50 from the rotational speed and the above-mentioned current value.

[0091] When the control device 90 is supplying power to the electric motor 40, in the load estimation process, it calculates an estimated value based on the current value supplied to the electric motor 40 and the impact detected by the impact sensor IS. Specifically, the control device 90 estimates the load torque from the rotational speed of the output shaft 42 and the current value, and calculates an estimated value based on the acceleration detected by the impact sensor IS when the acceleration is greater than the specified acceleration. The specified acceleration is predetermined. The specified acceleration is determined for each drive unit A. For example, the specified acceleration is set to a value greater than the expected acceleration in the drive unit A where the specified acceleration is set.

[0092] <Effect of load estimation processing> In the drive system 30, the control device 90 calculates an estimated value of the load on the reduction gear 50 by load estimation processing, both during periods when power is supplied to the electric motor 40 and during periods when power is not supplied to the electric motor 40. For example, when an excavator 100 is transported from a storage location to a work location by a transport vehicle, shocks caused by vibrations of the transport vehicle may act on the reduction gear 50 or the object to be driven. In this case, the control device 90 calculates an estimated value of the load torque acting on the reduction gear 50 or the object to be driven based on the shock input from the shock sensor IS.

[0093] <Effects of the First Embodiment> The effects of this embodiment will now be explained. (1-1) The drive system 30 generates heat in the electric motor 40 while keeping the object to be driven within a predetermined range of rotation through the warm-up process of the control device 90. The heat from the electric motor 40 is transferred to the reduction gear 50 connected to the electric motor 40. The drive system 30 of the excavator 100 can supply power to the electric motor 40 until the reduction gear 50 reaches a specified temperature while keeping the rotation of the object to be driven within a predetermined range. As a result, the drive system 30 can keep the reduction gear 50 above a predetermined specified temperature. Therefore, the drive system 30 can reduce the load on the reduction gear 50.

[0094] (1-2) The drive system 30 can perform warm-up processing by the control device 90 for each reduction gear 50. That is, if the temperature detected by the temperature sensor TS is different for each reduction gear 50, the drive system 30 can, for example, perform warm-up processing only for some of the reduction gears 50 that should be warmed up. Therefore, the power required for warm-up processing can be reduced compared to when warm-up processing is performed uniformly for all reduction gears 50.

[0095] (1-3) When power is not supplied to the electric motor 40, the drive system 30 calculates an estimated value of the load on the reduction gear 50 or the driven object based on the impact detected by the impact sensor IS through load estimation processing in the control device 90. In other words, the drive system 30, equipped with an impact sensor IS, can calculate an estimated value of the load generated on the reduction gear 50 or the driven object when the electric motor 40 is not rotating by performing load estimation processing in the control device 90. Thus, the drive system 30 can estimate the load on the reduction gear 50 or the driven object when the electric motor 40 is not rotating.

[0096] (1-4) When the drive system 30 is not supplying power to the electric motor 40, it calculates an estimated value of the load on the reduction gear 50 based on the impact detected by the impact sensor IS. On the other hand, when power is supplied to the electric motor 40, it calculates an estimated value of the load on the reduction gear 50 based on the current value supplied to the electric motor 40. In this way, the drive system 30 can estimate the load on the reduction gear 50 or the object to be driven by the load estimation processing of the control device 90, regardless of whether power is being supplied to the electric motor 40 or not.

[0097] (1-5) The impact sensor IS operates using the auxiliary battery 33 as a power source. By operating the impact sensor IS with the auxiliary battery 33, which is different from the battery 31, the drive system 30 can estimate the load on the reduction gear 50 or the driven object even when the control device 90 is not controlling the power output from the battery 31.

[0098] (1-6) The drive system 30 is equipped with an impact sensor IS, which is an acceleration sensor, and the control device 90 calculates an estimated value of the load on the reduction gear 50 or the object to be driven based on the acceleration detected by the impact sensor IS. The drive system 30 can detect impacts on the reduction gear 50 or the object to be driven with greater accuracy compared to, for example, a case in which a strain sensor is equipped as the impact sensor IS.

[0099] (1-7) When the control device 90 is supplying power to the electric motor 40, in the load estimation process, it calculates an estimated value based on the current value supplied to the electric motor 40 and the impact detected by the impact sensor IS. For example, if a strong impact is applied to the electric motor 40 from the outside during operation, causing the output shaft 42 to rotate in the opposite direction to the direction defined by the current value, it may become difficult to calculate the load estimate based on the current value. Even in this case, the control device 90 can calculate the estimated value because it performs load estimation processing based on the impact detected by the impact sensor IS.

[0100] <Second Embodiment> The following describes one embodiment of the drive system for a work machine. The drive system for the work machine in this embodiment is the drive system 30 for an excavator 100, similar to the first embodiment. The main difference from the first embodiment is that the drive unit A is equipped with a thermal transistor 110. For this reason, a detailed explanation of the same configuration as in the first embodiment will be omitted.

[0101] <Thermal transistor> As shown in Figure 5, the drive system 30 is equipped with a thermal transistor 110. The thermal conductivity of the thermal transistor 110 changes when an electric current is applied. The thermal transistor 110 may be a so-called all-solid-state transistor, or it may be a thermal transistor fluid consisting of an electrolyte sealed in a container. The drive system 30 is equipped with a thermal transistor 110 in each of the multiple drive units A. In other words, the drive system 30 is equipped with a thermal transistor 110 for each drive unit A. Note that the clutch mechanism 80 is not shown in Figure 5.

[0102] The thermal transistor 110 is interposed between the electric motor 40 and the gearbox 50. The thermal transistor 110 is fixed to the motor housing 41 and the gear housing 51, respectively. The motor housing 41 and the gear housing 51 are connected via the thermal transistor 110. Therefore, the heat generated by the electric motor 40 is transferred to the gearbox 50 via the output shaft 42 and the thermal transistor 110.

[0103] The thermal transistor 110 passes through the output shaft 42 of the electric motor 40. In other words, the output shaft 42 of the electric motor 40 is connected to the reduction mechanism 52. The thermal transistor 110 can be switched between a high thermal conductivity state and a low thermal conductivity state. In the high thermal conductivity state, the thermal conductivity of the thermal transistor 110 is higher than that of the output shaft 42 of the electric motor 40. Here, thermal conductivity is expressed, for example, in watts per meter per kelvin (W / m·K) in the International System of Units.

[0104] When the thermal transistor 110 is in a high thermal conductivity state, the heat generated by the electric motor 40 is transferred to the reduction gear 50 mainly via the thermal transistor 110. In a low thermal conductivity state, the thermal conductivity of the thermal transistor 110 is lower than that of the thermal transistor 110 in a high thermal conductivity state. When the thermal transistor 110 is in a low thermal conductivity state, the heat generated by the electric motor 40 is transferred to the reduction gear 50 mainly via the output shaft 42.

[0105] The thermal transistor 110 is connected to both the battery 31 and the control device 90. The control device 90 outputs a control signal to the thermal transistor 110 via the warm-up unit 94. The thermal transistor 110 switches between a high thermal conductivity state and a low thermal conductivity state based on the control signal input from the warm-up unit 94. Specifically, the control device 90 switches the thermal transistor 110 to the high thermal conductivity state during the warm-up process, and to the low thermal conductivity state otherwise.

[0106] The warm-up unit 94 switches the state of the thermal transistor 110 by controlling the power supply from the battery 31 to the thermal transistor 110. More specifically, the warm-up unit 94 puts the thermal transistor 110 into a high thermal conductivity state by connecting the thermal transistor 110 to the battery 31. Conversely, the warm-up unit 94 puts the thermal transistor 110 into a low thermal conductivity state by disconnecting the connection between the thermal transistor 110 and the battery 31.

[0107] <Operation of the second embodiment> The operation of this embodiment will now be explained. The control device 90 switches the thermal transistor 110 to a high thermal conductivity state during the warm-up process. When the warm-up process is not being performed, the control device 90 keeps the thermal transistor 110 in a low thermal conductivity state, and switches the thermal transistor 110 to a high thermal conductivity state when the warm-up process is being performed. When the temperature detected by the temperature sensor TS is below a specified temperature, the control device 90 performs the warm-up process and switches the thermal transistor 110 to a high thermal conductivity state. As a result, the heat generated by the electric motor 40 during the warm-up process heats the reduction gear 50 via the thermal transistor 110 in the high thermal conductivity state and the output shaft 42.

[0108] <Effects of the second embodiment> The effects of this embodiment will now be explained. (2-1) The drive system 30 can control heat conduction from the electric motor 40 to the reduction gear 50 by equipping it with a thermal transistor 110. When the temperature of the reduction gear 50 detected by the temperature sensor TS is below a specified temperature, the control device 90 can perform a warm-up process while the thermal transistor 110 is in a high thermal conductivity state. As a result, the drive system 30 of the excavator 100 can increase the rate at which the reduction gear 50 heats up due to the warm-up process compared to when the thermal transistor 110 is not equipped. On the other hand, when the warm-up process is not being performed, the control device 90 switches the thermal transistor 110 to a low thermal conductivity state, thereby preventing excessive heat from the electric motor 40 from being transferred to the reduction gear 50.

[0109] <Third Embodiment> The following describes one embodiment of the drive system for a work machine. The drive system for the work machine in this embodiment is the drive system 30 for an excavator 100, similar to the first and second embodiments. The main difference from the first and second embodiments is that the drive unit A is equipped with a heat transfer shaft 120. For this reason, a detailed explanation of the same configuration as in the first embodiment will be omitted.

[0110] <Electric motor> As shown in Figure 6, the electric motor 40 comprises a heat transfer shaft 120 and a shaft drive unit 121. The thermal conductivity of the heat transfer shaft 120 is higher than that of the output shaft 42. Here, thermal conductivity is expressed, for example, in watts per meter per kelvin (W / m·K) in the International System of Units. The output shaft 42 of the electric motor 40 has a through hole 43 that extends in the axial direction of the output shaft 42. The through hole 43 opens towards the inside of the motor housing 41 at one end of the output shaft 42 and towards the inside of the gear housing 51 at the other end. Therefore, the inside of the motor housing 41 and the inside of the gear housing 51 are in communication through the through hole 43 of the output shaft 42. Note that the clutch mechanism 80 is not shown in Figure 6.

[0111] <Heat transfer axis> The drive system 30 includes, in each of the multiple drive units A, a heat transfer shaft 120 and a shaft drive unit 121 corresponding to the heat transfer shaft 120. In other words, the drive system 30 includes a set of a heat transfer shaft 120 and a shaft drive unit 121 for each drive unit A.

[0112] The heat transfer shaft 120 is cylindrical. The base end of the heat transfer shaft 120 is connected to the shaft drive unit 121. The end of the heat transfer shaft 120 opposite to the base end is the tip end 123. The shaft drive unit 121 is housed in the motor housing 41. The shaft drive unit 121 is fixed to the motor housing 41.

[0113] The tip portion 123 of the heat transfer shaft 120 is configured to reciprocate along the axis J. Specifically, the heat transfer shaft 120 is reciprocable along the axis J with respect to the shaft drive unit 121. The reciprocating motion of the heat transfer shaft 120 along the axis J is driven by the shaft drive unit 121. An example of the shaft drive unit 121 is a solenoid. In this case, when current flows through the solenoid shaft drive unit 121, the heat transfer shaft 120 moves along the shaft drive unit 121. On the other hand, when the current to the shaft drive unit 121 is interrupted, the heat transfer shaft 120 moves in the opposite direction to when current flows through the shaft drive unit 121 due to an elastic force such as a spring.

[0114] The heat transfer shaft 120 can be switched between an inserted state and an uninserted state. By reciprocating the tip portion 123 along the axis J, the heat transfer shaft 120 switches between the inserted state and the uninserted state.

[0115] In the inserted state, the tip 123 of the heat transfer shaft 120 is located inside the gear housing 51. In other words, the heat transfer shaft 120 in the inserted state reaches the inside of the gear housing 51. The heat transfer shaft 120 in the inserted state penetrates the output shaft 42. Figure 6 shows the heat transfer shaft 120 in the inserted state. The heat transfer shaft 120 penetrates the output shaft 42, and its tip 123 protrudes into the space in the gear housing 51 where the lubricant 52a is stored.

[0116] When the heat transfer shaft 120 is inserted, the heat generated by the electric motor 40 is transferred to the reduction gear 50 via the motor housing 41, the output shaft 42, and the heat transfer shaft 120. The heat transferred to the reduction gear 50 via the heat transfer shaft 120 heats the lubricant 52a after being transferred to the heat transfer shaft 120, without the need for other components.

[0117] In the non-inserted state, the tip 123 of the heat transfer shaft 120 is located outside the gear housing 51. When the heat transfer shaft 120 is not inserted, the heat generated by the electric motor 40 is transferred to the reduction gear 50 via the motor housing 41 and the output shaft 42. In Figure 6, the position of the tip 123 of the heat transfer shaft 120 in the non-inserted state is indicated by a dashed line on the heat transfer shaft 120.

[0118] The heat transfer shaft 120 is connected to the control device 90 via the shaft drive unit 121. The control device 90 outputs a control signal to the shaft drive unit 121 via the warm-up unit 94. Based on the control signal input from the warm-up unit 94, the shaft drive unit 121 switches the state of the heat transfer shaft 120 between an inserted state and an uninserted state. In other words, the heat transfer shaft 120 reciprocates inside the motor housing 41 along the axis J in response to the control signal from the warm-up unit 94. For example, the control device 90 moves the heat transfer shaft 120 along the axis J by supplying power to the shaft drive unit 121. Specifically, during the warm-up process, the control device 90 switches the heat transfer shaft 120 to the inserted state through the control of the shaft drive unit 121, and otherwise switches the heat transfer shaft 120 to the uninserted state through the control of the shaft drive unit 121.

[0119] <Operation of the third embodiment> The operation of this embodiment will now be explained. The control device 90 switches the heat transfer shaft 120 to the inserted state during the warm-up process. More specifically, the control device 90 keeps the heat transfer shaft 120 in the uninserted state when the warm-up process is not being performed, and switches the heat transfer shaft 120 to the inserted state when the warm-up process is being performed. The control device 90 performs the warm-up process and switches the heat transfer shaft 120 to the inserted state when the temperature detected by the temperature sensor TS is below a specified temperature. As a result, during the warm-up process, the heat generated by the electric motor 40 is directly transferred to the inside of the gear housing 51 by the tip 123 of the heat transfer shaft 120. The heat generated by the electric motor 40 is transferred to the motor housing 41 and the output shaft 42, as well as to the reduction gear 50 via the heat transfer shaft 120, which has higher thermal conductivity than the output shaft 42.

[0120] <Effects of the Third Embodiment> The effects of this embodiment will now be explained. (3-1) In the drive system 30, the heat generated by the electric motor 40 is transferred to the reduction gear 50 via the heat transfer shaft 120, in addition to the output shaft 42 of the electric motor 40. Since the heat transfer shaft 120 is made of a material with higher thermal conductivity than the material of the output shaft 42 of the electric motor 40, it is capable of greater heat transfer than the output shaft 42. In other words, the drive system 30 can transfer the heat from the electric motor 40 to the reduction gear 50 more efficiently than if the heat transfer shaft 120 were not provided. As a result, the drive system 30 can reduce the load on the reduction gear 50 more efficiently.

[0121] (3-2) During the warm-up process, the drive system 30 can directly heat the inside of the gear housing 51 with the tip 123 of the heat transfer shaft 120. <Example of changes> Furthermore, each of the above embodiments can be implemented with the following modifications. The above embodiments and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0122] The control device 90 does not need to perform a warm-up process independently for each of the electric motors 40. For example, the control device 90 may perform a warm-up process uniformly for all of the electric motors 40. In this case, it is preferable that the control device 90 cools the reduction gear 50, which has been overheated by the warm-up process, using the cooling device 60.

[0123] The drive system 30 may be equipped with a temperature sensor TS in at least one of the multiple reduction gears 50. For example, the drive system 30 may be equipped with a temperature sensor TS in the reduction gear 50 of the drive unit A that is used most frequently among the multiple drive units A.

[0124] The drive system 30 may include both a thermal transistor 110 and a heat transfer shaft 120. In this case, the control device 90 switches the thermal transistor 110 to a high heat conduction state and switches the heat transfer shaft 120 to an inserted state during the warm-up process. As a result, the heat generated in the electric motor 40 is transferred to the reduction gear 50 via the motor housing 41, output shaft 42, thermal transistor 110, and heat transfer shaft 120.

[0125] In the second embodiment, the control device 90 may switch the thermal transistor 110 from a low thermal conductivity state to a high thermal conductivity state even when warm-up processing is not being performed. For example, the control device 90 may perform the above switching according to the magnitude of the torque output by the electric motor 40.

[0126] The control device 90 can control the total heat capacity of the unit consisting of the electric motor 40 and the reduction gear 50 by controlling the state of the thermal transistor 110. Specifically, the control device 90 can increase the total heat capacity of the unit by switching the thermal transistor 110 from a low thermal conductivity state to a high thermal conductivity state. In the excavator 100, for example, when performing excavation work, the torque output by the electric motor 40 may be increased in a short period of time. This may cause the electric motor 40 to heat up rapidly, but the drive system 30 can suppress heat retention in the electric motor 40 by efficiently transferring heat from the electric motor 40 to the reduction gear 50.

[0127] The cooling device 60 may be configured to cool the reduction gear 50 and the electric motor 40. The control device 90 may switch the brake device 70 to a restricted state during the warm-up process. In this case, when the warm-up process is performed on the drive unit A, if the brake device 70 of the drive unit A is in a permitted state, the control device 90 switches the brake device 70 to a restricted state using the operation control unit 93, and then performs the warm-up process using the warm-up unit 94. According to this, the control device 90 switches the brake device 70 to a restricted state during the warm-up process to restrict the rotation of the restricted shaft 71. In other words, the control device 90 performs the warm-up process with the rotation of the output shaft 42 of the electric motor 40 restricted. In the drive system 30, the heat transferred to the reduction gear 50 is generated by the electric motor 40 whose rotation is restricted by the brake device 70. The electric motor 40 can convert the supplied power into heat more efficiently than when rotation is permitted. As a result, the drive system 30 can efficiently warm up the reduction gear 50 by restricting the rotation of the electric motor 40 with the brake device 70 while performing the warm-up process of the control device 90.

[0128] Furthermore, the control device 90 does not need to switch the brake device 70 to the restricted state during the warm-up process. For example, during the warm-up process, the brake device 70 may be switched by the operator of the excavator 100.

[0129] The regulated shaft 71 may also be the output member 53. The position of the brake device 70 in the drive unit A is not limited to the embodiment. For example, the brake device 70 may be interposed between the motor housing 41 and the object to which the motor housing 41 is attached. In short, the brake device 70 only needs to be able to restrict the rotation of the restricted shaft 71 selected from the output shaft 42 of the electric motor 40 and the output member 53 of the reduction gear 50.

[0130] The control device 90 may switch the clutch mechanism 80 to a disengaged state during the warm-up process. When the control device 90 is performing a warm-up process on the drive unit A and the clutch mechanism 80 of the drive unit A is engaged, the operation control unit 93 switches the clutch mechanism 80 to a disengaged state, and then the warm-up unit 94 performs the warm-up process. As described above, when the control device 90 performs a warm-up process on the drive unit A, it switches the state of the brake device 70 and the clutch mechanism 80 in the drive unit A so that the object to be driven does not rotate due to the rotation of the output shaft 42 of the electric motor 40. Note that the control device 90 does not have to switch the clutch mechanism 80 to a disengaged state during the warm-up process. For example, during the warm-up process, the clutch mechanism 80 may be switched by the operator of the excavator 100.

[0131] The control device 90 may rotate the output shaft 42 of the electric motor 40 within a predetermined range using the warm-up unit 94 during the warm-up process. In other words, the control device 90 may operate the electric motor 40 and the reduction gear 50 in the drive unit A during the warm-up process of the drive unit A. The predetermined range in which the output shaft 42 of the electric motor 40 rotates is defined such that the rotation angle of the output member 53 of the reduction gear 50 is within a predetermined range. The drive system 30 operates the reduction gear 50 during the warm-up process by the control device 90, thereby guiding the flow of the lubricant 52a through the reduction mechanism 52. The flow of the lubricant 52a during the warm-up process stirs up heat within the lubricant 52a. In other words, the drive system 30 can heat the lubricant 52a more efficiently by operating the reduction gear 50 during the warm-up process by the control device 90 compared to, for example, the case where the lubricant 52a remains stationary. As a result, the drive system 30 can raise the lubricant 52a of the reduction gear 50 to the specified temperature more quickly.

[0132] The control device 90 does not necessarily have to perform processing based on command signals input from the operator, with each of its operation control unit 93, warm-up unit 94, and load estimation unit 95 performing processing based on the operation control unit 93, warm-up unit 94, and load estimation unit 95 performing processing according to a predetermined schedule.

[0133] An example of the control device 90 executing the warm-up unit 94 according to a predetermined schedule will be described. The schedule is set based on a work schedule that defines the tasks to be performed by the excavator 100 in chronological order. For example, consider a work schedule in which the excavator 100 moves from the storage area to the work area and performs excavation work. In this case, the excavator 100 moves from the storage area to the work area using the travel device 12, and then operates the work attachment 20 to perform excavation work.

[0134] In the above work schedule, the excavator 100 first drives the travel drive unit A5 after starting up. Therefore, the control device 90 performs a warm-up process on the reduction gears 50 of each of the travel drive unit A5 and the slewing drive unit A6. The excavator 100 travels towards the work site after the temperature of the reduction gears 50 of each of the travel drive unit A5 and the slewing drive unit A6 exceeds the specified temperature. After the excavator 100 reaches the work site, the control device 90 performs a warm-up process on the reduction gears 50 of each of the first to fourth drive units A1 to A5. The control device 90 may also perform a warm-up process on the reduction gears 50 of each of the first to fourth drive units A1 to A4 while the excavator 100 is traveling towards the work site. As a result, the excavator 100 can perform excavation work at the work site with the temperature of the reduction gears 50 of each drive unit A above the specified temperature. As described above, the drive system 30 of the excavator 100 can independently warm up multiple reduction gears 50 according to a preset schedule using the control device 90. As a result, the drive system 30 of the excavator 100 can efficiently warm up multiple reduction gears 50.

[0135] The impact sensor IS is not limited to an acceleration sensor. For example, the impact sensor IS may be a strain sensor that detects strain in the reduction gear 50 as an impact. The configuration of the auxiliary battery 33 is not limited to that of the embodiment. The auxiliary battery 33 may be separate from the battery 31. For example, the drive system 30 may have one auxiliary battery 33 and supply power to multiple impact sensors IS from this one auxiliary battery 33.

[0136] The drive system 30 does not necessarily have to include an auxiliary battery 33. In this case, the impact sensor IS is powered by the battery 31. The control device 90 does not need to calculate the estimated value based on the current value supplied to the electric motor 40 during the load estimation process. In this case, the control device 90 calculates the estimated value based on the impact detected by the impact sensor IS, regardless of whether power is supplied to the electric motor 40 or not.

[0137] • The work equipment is not limited to the excavator 100. The work equipment may be any construction machine other than the excavator 10. Furthermore, the work equipment is not limited to construction machines. Examples of work equipment other than construction machines include machines used in forestry, quarrying, industrial waste treatment, and agriculture.

[0138] In the above embodiment, a structure composed of multiple objects may be integrated, or conversely, a structure composed of a single object may be divided into multiple objects. Whether or not the objects are integrated, the structure should be configured in a way that achieves the objective of the invention.

[0139] In the above embodiment, if multiple functions are provided in a distributed manner, some or all of those multiple functions may be consolidated and provided together. Conversely, if multiple functions are consolidated and provided together, some or all of those multiple functions may be distributed and provided together. Regardless of whether the functions are consolidated or distributed, it is sufficient that the device is configured to achieve the objective of the invention.

[0140] The control device 90 may calculate an estimated value in the load estimation process without relying on the impact detected by the impact sensor IS when supplying power to the electric motor 40. In other words, the control device 90 may calculate an estimated value based on the impact detected by the impact sensor IS only when power is not being supplied to the electric motor 40.

[0141] The impact sensor IS may detect the acceleration of the driven object as an impact. The impact sensor IS may be attached to the object being driven. The position where the impact sensor IS is attached to the object being driven is set according to the type of object being driven and the type of impact to be detected by the impact sensor IS. For example, if the impact sensor IS is attached to the arm 23 and the impact sensor IS detects an impact acting between the arm 23 and the boom 21, the impact sensor IS is attached to the part of the arm 23 closer to the first arm end 23A.

[0142] Multiple impact sensors IS may be attached to a single driven object. For example, if three impact sensors IS are attached to the arm 23, it is preferable that the impact sensors IS be attached to the first arm end 23A, the central part of the arm 23 in the longitudinal direction, and the second arm end 23B of the arm 23.

[0143] The drive system 30 may include a notification unit connected to the control device 90. An example of a notification unit is an output terminal such as a display located in the cabin. The control device 90 may output the estimated value calculated by the load estimation unit 95 to the output terminal. Alternatively, the control device 90 may store the estimated value in memory 91 after calculating it. For example, when performing maintenance on the excavator 100, the operator may refer to the estimated value stored in memory 91 to understand the status of multiple drive units A.

[0144] The control device 90 may calculate diagnostic information related to the excavator 100 from estimated values. For example, the control device 90 may estimate when maintenance will be required for the excavator 100 by combining the estimated values ​​from multiple reduction gears 50. The estimated values ​​from multiple drive units A and the corresponding time for the excavator 100 are associated, for example, with a table created by simulation.

[0145] • Incidentally, the construction machine disclosed in Japanese Patent Publication No. 2003-082707 uses an electric cylinder with a built-in reduction gear. The electric cylinder is installed in the construction machine to drive, for example, the boom, arm, and bucket. Furthermore, Japanese Patent Publication No. 2019-049532 discloses an induction motor and a method for diagnosing mechanical elements connected to the induction motor. This diagnostic method obtains the torque value in the induction motor from the current value detected in the induction motor. The induction motor is diagnosed using the obtained torque value as a diagnostic index.

[0146] In the conventional work machines described above, shocks may be applied to the reduction gear or the object driven by the reduction gear even when power is not supplied to the electric motor. However, in the drive systems of conventional work machines, the load on the reduction gear or the object driven can only be estimated when power is supplied to the electric motor.

[0147] Even when power is not supplied to the electric motor, the warm-up process described in the above embodiment is not essential from the standpoint of estimating the load on the reduction gear or the object driven by the reduction gear. In this case, the control device 90 only needs to be capable of performing load estimation processing.

[0148] <Note> The technical concepts that can be understood from each of the above embodiments and their modifications are described below. <Note 1> A drive system for a work machine comprising: an electric motor which is a drive source for a rotating object to be driven; a reduction gear which amplifies the torque of the electric motor and outputs it to the object to be driven; a control device which controls the power supply to the electric motor; and an impact sensor for detecting impacts, wherein the control device performs a load estimation process which calculates an estimated value of the load on the reduction gear or the object to be driven, and when power is not supplied to the electric motor, in the load estimation process which calculates the estimated value based on the impact detected by the impact sensor.

[0149] <Note 2> The control device, when supplying power to the electric motor, calculates the estimated value in the load estimation process based on the current value supplied to the electric motor, according to the drive system for the work machine described in Appendix 1.

[0150] <Note 3> A drive system for a work machine according to Appendix 1 or Appendix 2, comprising a battery for supplying power to the electric motor, and an auxiliary battery, separate from the battery, for supplying power to the impact sensor.

[0151] <Note 4> The drive system for a work machine as described in any one of Appendix 1 to Appendix 3, wherein the impact sensor is an acceleration sensor that detects the acceleration of the reduction gear or the object to be driven as the impact. [Explanation of symbols]

[0152] 30…Drive System 40…Electric motor 42…Output shaft 50...Reducer 51... Gear housing as a housing 53…Output component 70…Brake system 71...Axis subject to regulation 80...Clutch mechanism 90...Control device TS... Temperature sensor 100... Excavators as work machines 110... Thermal transistor 120... Heat transfer shaft 123...Tip

Claims

1. Electric motor and, A reduction gear is connected to the aforementioned electric motor and amplifies the torque of the electric motor and outputs it to the object to be driven, A control device that controls the power supply to the electric motor, The system includes a temperature sensor for detecting the temperature of the reduction gear, The control device is If the temperature detected by the temperature sensor is below a predetermined specified temperature, a warm-up process is performed to supply power to the electric motor and generate heat, while keeping the rotation angle of the output shaft of the reduction gear within a predetermined range. A drive system for industrial machinery.

2. The aforementioned reduction gear has a housing, The electric motor has a heat transfer shaft that extends coaxially with the output shaft of the electric motor and passes through the output shaft of the electric motor. The heat transfer shaft extends into the interior of the housing. The thermal conductivity of the heat transfer shaft is higher than that of the output shaft of the electric motor. A drive system for a work machine according to claim 1.

3. The heat transfer shaft can be switched between an inserted state in which its tip is located inside the housing, and an uninserted state in which its tip is located outside the housing. The control device switches the heat transfer shaft to the inserted state during the warm-up process. The drive system for the work machine according to claim 2.

4. It has a thermal transistor interposed between the electric motor and the reduction gear, The thermal transistor can be switched between a high thermal conductivity state, which has higher thermal conductivity than the material of the output shaft of the electric motor, and a low thermal conductivity state, which has lower thermal conductivity than the high thermal conductivity state. The control device switches the thermal transistor to the high thermal conductivity state during the warm-up process. A drive system for a work machine according to claim 1.

5. When one of the output shafts of the electric motor and the output member of the reduction gear is selected as the shaft to be restricted, the brake device is equipped with a switchable state in which it contacts the shaft to be restricted and restricts the rotation of the shaft to be restricted, and a state in which it allows the rotation of the shaft to be restricted. The control device switches the brake device to a restricted state during the warm-up process. A drive system for a work machine according to any one of claims 1 to 4.

6. It comprises a plurality of electric motors, a plurality of reduction gears corresponding to each of the plurality of electric motors, and a plurality of temperature sensors corresponding to each of the plurality of reduction gears, The control device performs the warm-up process independently for each of the electric motors. The drive system for the work machine according to claim 5.

7. A clutch mechanism interposed between the electric motor and the reduction gear is provided, which can be switched between a disengaged state that disconnects the electric motor and the reduction gear, and an engaged state that allows the transmission of torque from the electric motor to the reduction gear. The control device switches the clutch mechanism to the disengaged state during the warm-up process. The drive system for the work machine according to claim 5.

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